Indicating systems for vertical lifting apparatus



May 29, 1962 J. E. SMITH ETAL 2 Sheets-Sheet 1 Filed Nov.

United States Patent ware Filed Nov. 9, 1959, Ser. No. 852,590 11 Claims. (Cl. 187-9) This invention relates to apparatus for graphically recording the operations of a vehicle and has for an object the provision of a system by means of which there may be recorded the number of pay loads lifted by the vehicle during and in correlation with the distance traveled by the vehicle and in avoidance of the recording of apparent pay-load lifts which, in fact, have not taken place.

This application is a continuation-in-part of our application Serial No. 689,700, filed October 11, 1957 and now abandoned.

Lift trucks and similar equipment used in handling industrial materials play a very important part in the operation of factories in that assembly lines and the like frequently depend upon lift trucks for the transport of parts and equipment from storage to assembly line and the transport of finished products to storage. Trucks of the fork-lift type, as Well as tractor-shovels, earth movers, and like hydraulically operated lift Vehicles play an important part in construction, as well as in moving materials from one place to another. The efficiency of an operation as a whole can be greatly increasedif the operators of lift trucks and similar equipment function with maximum efficiency and with elimination of waste motion, excess travel and inefficient loading.

Though not limited thereto, the present invention is particularly applicable to fork-lift trucks and similar equipment widely used in close quarters, such as warehouses, boxcars, dock installations, ships, and in factories as described above. As well understood by those skilled in the art, the lift truck is designed so that it may lower its lifting platform or its lifting fork for movement beneath a pay load. By pay load, we mean a useful load in contrast with what in terms of recording equipment may be referred to as apparent or spurious loads or load indications. After placement of the platform or fork beneath a container or below the work itself, the load is then raised and transported to an assigned delivery point. The load is there lowered, and the operator proceeds to the next station, either with or without a further pay load. When an operator is serving presses or other types of machinery, he will frequently take raw material to the machine for operation and remove a finished or semifinished product. In this manner, the truck is used to maximum eflicienc It is an object of our invention to provide a record not only of the distance traveled by the truck, but also an accurate record of the number of true pay load lifts completed during each trip by means of a system which eliminates the recording of false lifts, that is to say, the recording of a lift of a pay load which has not in fact taken place. In many instances, the forks and unloaded pallet associated therewith Weigh between about 150 pounds and 300 pounds. If a truck be operated to lift such unloaded pallet at relatively high speed, the actual weight will produce on the indicating equipment an apparent weight materially greater than that which actually exists, with the result that a lift may be falsely recorded. Another instance giving rise to difliculty is the fact that in operating a truck over rough terrain, a bump may cause a pay load to bounce. While it may not actually rise above the pallet on which it rests, the apparent weight on the truck will be greatly diminished and to a point where an unloading operation may be falsely recorded. This same phenomenon may likewise produce an apparent increase in weight in the case of an unloaded pallet and by an amount which likewise may indicate a lifting operation. These examples suffice to illustrate the problems encountered in obtaining accurate information in respect to the number of pay loads lifted for a given trip of the vehicle in order that there may be achieved the maximum efficiency of use of the vehicular lifting apparatus.

In accordance with the present invention, there is provided, in conjunction with the hydraulic system for raising and lowering the lifting forks or platform, a pressure-responsive means having an element displaceable from an unloading position to a loaded position upon a substantial increase of pressure on the hydraulic liquid as occurs upon the lifting of a pay load. In order to prevent the operation of exhibiting means operable under the control of that element by any cause other than the lifting of a pay load, there is arranged a delay means for retarding the movement of the element both from its loaded position and from its unloaded position as a result of transient changes in the pressure of the hydraulic liquid. By transient changes, we mean changes in the pressure of the hydraulic liquid which may arise due to abnormal or improper lifting of a platform by its hydraulic operator, or due to passage over bumps as previously referred to, or other operations which may produce to some degree the effect of lifting or releasing a pay load when in fact no true lift or release of a pay load has occurred. The transient changes of pressure will vary in character and magnitude with different lift trucks. Accordingly, the lift-delays and the off-delays will be selected for best operation of a particular system as used on the several types of lift trucks. The time-delays may vary through wide ranges, as from two to thirteen seconds, more or less. The lift-delay may be in the range of from two to four and one-half seconds, with the offdelay between ten to thirteen seconds. However, the offdelay will preferably be from three to five times the liftdelay, though in some cases the off-delay setting may be less than the setting for the lift-delay.

The exhibiting means preferably includes a chart to receive ;a permanent record of each pay load lift and in correlation with a second record showing the distance traveled by the vehicle during the time it is operated to lift pay loads and to lower said payloads at particular destinations or stations. The exhibiting means is arranged to be operated, either with or without access thereto by the operator of the vehicle, to provide a record which may not be known to the operator until the conclusion of a particular period of work.

For further objects and advantages of our invention, reference is to be had to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 schematically illustrates an exemplary embodiment of the invention; and

FIG. 2 is a view of the cover of the instrument diagrammatically shown in FIG. 1 and includes a face view of the chart, together with a portion of the timing mechanism for driving the chart.

Referring now to FIGS. 1 and 2, the invention in one form has been shown applied to a lift truck 10 which includes a fork or lifting platform 11 arranged to he raised and lowered by hydraulic means 12 of conventional design. The operator of the truck It) by means of .1 control valve 13 may apply the output of a pump 14 to the lifting cylinder of the hydraulic operating means 12 to raise the platform 11. By rotating the control valve 13, he may connect the hydraulic lifting means to the discharge pipe 15 leading to a reservoir 16. It will be readily understood by those skilled in the art that the pressure developed by the hydraulic liquid will depend upon the load resting upon the platform 11. In addition, the apparent load will be increased by reason or the inertia of the parts, particularly when the hydraulic operator 12 is raising the platform 11 at substantial speed.

In accordance with the present invention, there is pro vided a pressure-responsive device 17 flow-connected to the hydraulic system, preferably by way of a throttling valve 18 shown as of the needle-valve type. The needle valve 18 serves as a filter and removes high-frequency pressure-variations which may appear in the hydraulic system connected to operator 12. The hydraulic pressure developed at the output of the pump 14 for operator 12 is also applied to a piston 19 of the pressure-responsive device 17. When that pressure exceeds a predetermined value, the piston 19 overcomes the opposing bias of a spring 20 to close a switch 21. The opposing pressure of spring 20 may be adjusted by rotating a cap 2'2. to change the initial force developed by the spring 29 on piston 19. Preferably, spring 20 is adjusted so as to render piston 19 ineffective to close switch 211 unless the pressure on the system exceeds a predetermined minimum corresponding to the weight of forks or platform 11 when empty, or when carrying merely an unloaded pallet. Such predet termincd minimum, however, may be less than the apparent load that may be developed during lifting of an empty platform or unloaded pallet. By apparent load, we mean the load as it appears to the lift sensing mechanism, including an inertia component due to acceleration in case the predetermined minimum load is lifted at relatively high speed (in terms of maximum speed of lift of the lifting fork or platform in normal operation), Hence, notwithstanding adjustment of spring 20' as above described, such apparent load may be sufiicient to effect operation of piston 19 to close switch 21. Recording of a false lift under such circumstances, however, may be avoided by provision of a suitable delay factor as more fully described hereinafter.

When a true pay load is being lifted, the piston 19 will close switch 21 to complete an energizing circuit for-a relay 25 which after a time delay closes its contacts 26. As diagrammatically illustrated, when relay 25 is energized, a tension spring 27 applies a closing force upon contact 26. This contact is restrained by a dashpot 28 which includes a piston 29 having an opening 30 therein normally closed by a flap valve 31. The speed of movement of the piston 29 and of contact 26 may be regulated by the setting of a throttling valve 3'2. In one embodiment of the mechanism of FIG. 1 as used in industrial plant material handling systems, the time-delay for the closing of the contacts 26 may, for example, range from two seconds to four and one-half seconds or more. This time-delay is important in order to avoid indications of false lifts, i.e., lift indications due to variations in pressure on the hydraulic liquid as the result of causes other than the lifting of true pay loads.

Upon expiration of the selected time interval, the circuit through the contacts 216 is completed to energize a relay 35 which immediately completes a circuit through its contacts 36. This relay includes a dashpot 37 having a piston 38, a flap valve 39, a tension spring 40, and a throttling valve 41'for producing a time-delayed opening of the circuit through its contacts 36. While the energizing circuits for the relays 2-5-and 35 are readily traced by inspection between supply lines '43 and 44, it is to be noted that upon the closing of contacts 36, there is completed an energizing circuit for a solenoid operator 45 of the recording mechanism. This circuit may be traced from supply line 43 by way of conductor 46, contacts 36, conductor 47, the solenoid operator 45, and by conductor 48 to the other supply line 44. Whenever there is being recorded the lifting of a pay load, a signal lamp 49 (connected in shunt with the solenoid operator 45) is energized. This lamp when energized will illuminate a window 49a, FIG. 2, provided in the cover 64.

Upon energization of the solenoid operator 45, an attractive force isexented upon its associated armature 'ss which is rotated in a clockwise direction about its pivotally supported end 50a and against the bias of a spring 51. Through a link 52 the armature 5t) rotates a stylus arm 53 pivoted at one end at '54 to move its stylus 55 in a counterclockwise direction. Though markers of different types may be utilized, the stylus 55 has been shown in the form of a needlepointed stylus adapted to engage the coated surface of a chart se. Charts of this type are Well known to those skilled in the art and generally include a light coating of an opaque paraflin mixture or the like through which the stylus penetrates to produce a visual indication of the movement of the stylus. While the chart 56 is shown in phantom in FIG. '1, in order to show its positional relationship in respect to the stylus 55 and to needle pointed stylus 57, the chart itself is illustrated in FIG. 2. The records produced by the styli 55 and 5'7 appear within circular areas of the chart and may be in distinctive colors, the color of the paraffin-coated chart.

The chart 56 is driven at constant speed by a clock motor 59 in a counterclockwise direction as viewed in 'FIG. 2, the chart having a rectangular center opening which fits onto a correspondingly shaped section of a shaft 60 driven by the clock motor.

After the lifting of a pay load with resultant energization of solenoid operator 45 to move stylus 55 from an inner radial limit to an outer radial limit, it will be understood the stylus 55 produces an arcuate mark on the chart at the outer radial limit of length related to the duration of the pay load lift. When the pay load is iowered onto a load-receiving structure, the load on the lifting platform decreases to its unloaded weight. The reduction of hydraulic pressure on piston 19 permits spring 20 to open theswitch 21. Relay coil 25 is dcenergized and immediately opens since flap valve 31 is arranged so as not to offer resistance to downward movement of piston 29 of dashpot 28. Then, after a selected off-delay time afforded by dashpot $7, the contacts 36 of relay 35 open to deenergize solenoid operator $5. The stylus 55 is then moved by spring 51 and by gravity to its inner radial limit.

The foregoing operations will now be briefly summarized in terms of the resultant record on the chart 56, as shown in FIG. 2 At the beginning of a work period, it may be assumed that the point 55a on chart 56 was at the location of the stylus 55; that the stylus 57 Was at the point 57a; and that both styli were coincident with radius 61 of the chart 56. After the first lift of a pay load occurred, the stylus 55 moved radially of the chart to an outermost position at 55b. At the point 550, the stylus 55 returned to its innermost position 55d, indicating the unloading of the truck. By means of an odometer driving arrangement (later described) for the stylus 57, the distance traveled may be read either from the graph 57b on chart 56 or from a distance indicator 62 (FIG. 1) visible through the opening 62a of the cover 64 of the instrument housing '63. As shown on the chart, the truck traveled unloaded during the appearance of the segment 55d after which it made two pay load lifts in near time-proximity one to the other. The relatively long outer section 55c shows a relatively long distance of travel with a pay load. Thus, the chart 56 provides an accurate record of the number of lifts in correlation with the distance traveled by the truck with and without pay loads.

Referring again to FIG. 1, the odometer drive has been illustrated as including a friction wheel 70 driven by one of the wheels 71 of the lift truck 19. Through a suitable connection indicated by the broken line 72, there is driven a worm 73 which through worm wheel 74 drives a shaft 75. This shaft, through a worm 77, drives a worm wheel 76. The Worm wheel 76 drives a shaft 78 which has secured to it an operating cam '79 for a crank arm 80, one end of which carries the stylus 57. The other arm 81 of the crank engages the cam 7 9, the crank arm itself benig pivoted by a pin 82 and biased for clockwise rotation by a spring 83.

worm 85 which drives a worm wheel 86 and through a shaft 87 operates the distance indicator 62 illustrated as a conventional odometer provided with a plurality of indicating discs on which appear digits for indicating the distance traveled.

In the following summary of the operation of the invention, the manner in which it functions to take care of a number of conditions encountered in the daily operation of a lift truck will be set forth. There will first be summarized the operations which may occur with an unloaded platform, i.e., one not carrying a pay load. With the parts in the illustrated positions, particularly the valve 13 in a pressure-applying position, the hydraulic means 12 will be eifective in raising the movable parts of the hydraulic system including the platform 11. Thus, the parts will be moving upwardly. If the parts are moved upwardly at relatively high speed, the apparent load (previously discussed) as registered on the pressure-responsive device 17 may be much greater than the actual load. It is for this reason that weighing systems are not suited to the purposes of the present invention. Though the spring has been set to offset the pressure required from the pump 14 to overcome the dead weight of the moving parts, nevertheless upon rapid acceleration of the platform, the piston 19 will be displaced against the force of the spring 20 to close the contact 21. Though the operating coil of relay is thereby energized, its associated contacts 26 are not closed by reason of the delay introduced by the dashpot 28. This delay is preferably of an order which prevents closure of the circuit through switch contacts 26 for a time interval during which the unloaded platform 11 will be raised to a predetermined height, a height which would render the empty platform apparent to any observer. Should an operator desire to attempt to produce a false indication of a lift of a pay load, it will be seen that he could not achieve that objective without raising the platform 11 to a height which would undoubtedly call attention to his effort by the foreman or other assigned observer.

If desired, the delay means 28 for relay 25 may be set for a longer period of time, enough for the platform 11 to be raised to the normal height for transport of a pay load. Thus, there is considerable flexibility afiorded by the system in that there can be included in the delay time a part of the travel time, or that delay time may be diminished to a lifting time corresponding with that required for achieving the aforesaid detectable height of the platform 11.

Assuming now a The shaft 78 carries a pay load on the platform 11, the following occurs. The truck operator manipulates valve 13 to raise the pay load. After the selected time interval of, say, three seconds, the circuit through the contact 26 is closed to energize the coil of the relay 35. This relay immediately closes to energize the solenoid 45 to produce the indication on the chart 56 that a pay load has been lifted. The truck will then be placed in operation to transport the load to its destination, and there will be recorded on the chart as described above the record 57b indicating the distance traveled by the truck. It will be observed that the record 571) is one that progresses from an inner circular limit to an outer circular limit and back to the inner circular limit, this representing the movement of the stylus 57 by the cam 79. When the stylus has been displaced from the inner to the outer limit, is will be known that the truck has traveled a predetermined distance, for example, 2500 feet. When the stylus moves from the outer limit to the inner limit, it will be known that the truck has traveled another 2500 feet. Obviously, the gear ratios can be selected for the operation of the stylus between its two limits for lesser or greater distances.

What has been said above in respect to false indications of pay load lifts likewise applies to false indications of the unloading of the platform 11. This can occur by reason of the passage of the truck 10 over a rough travel path where the wheels of the truck may apply an upward acceleration to platform 11 which will result in an apparent decrease in the load on that platform. This will be reflected by momentary decrease in the hydraulic pressure. In response thereto, the switch 21 will open and so will the relay 25. The opening of the contacts 26, however, though they deenergize the operating coil of relay 35, does not result in opening of the circuit through its contacts 36. The time-delay opening of contacts 36, as determined by the setting of throttle valve 41, maintains energization of solenoid 45 and thus maintains the stylus 55 in a position indicating there is a pay load on platform 11. The time-delay for the opening of the contacts 36 in one industrial embodiment of the system of FIG. 1 is set for a delay of between ten seconds and thirteen seconds. It is to be understood, however, that delay times, for both lift-delay and off-delay, will be utilized depending upon the particular characteristics of the system and the conditions of operation of the lift truck 10. For some operations, the times may be quite short, and for other operations, the times will be increased to the upper limits or beyond in order to achieve accurate recording of pay load lifts, as well as the unloading of a load at a destination for the truck 10.

Further in connection with the operations, it will be understood that even if the truck 10 be traveling without a pay load over rough terrain, the effect of a bump may work in both directions; that is to say, the weight of the moving parts including the paltform 1 1 may be effective to produce a false indication of a pay load lift, as well as to indicate the unloading of a pay load, when a change in pressure occurs by reason of the inertia elfect of the load on the hydraulic pressure system. However, by the introduction of the time-delays, such false indications are overcome, whether due to an attempt by the operator to outwit the system, or whether due to variations of hydraulic pressure because of bumps and the like.

With further reference to the control valve 13, it is to be understood that it will be operable to several control positions. When it is moved to a position to interconnect the pump 14- with the discharge pipe 15, the pump will simply circulate hydraulic liquid from the reservoir 16 through the return circuit. There will be maintained closed the hydraulic system 12 thus to maintain the platform 11 in its elevated position. When the valve 13 is rotated to interconnect the hydraulic system 12 with the discharge pipe 15 (the valve 13 in a position from that illustrated), hydraulic liquid will be discharged through return pipe 15 from both the hydraulic system and from the pump 14.

Now that we have explained the principles of operation of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein and that certain features may be used in the absence of other features, all within the spirit and scope of the appended claims.

.What is claimed is:

1. In a load-lifting apparatus having a fixed frame, a load-supporting platform and hydraulic means including a hydraulic liquid for raising and lowering said platform relative to said fixed frame, the combination of pressureresponsive means including a device fluid-connected to said hydraulic means, said device having an element displaceable from an unloaded position to a loaded position upon a substantial increase of pressure on said hydraulic liquid as occurs upon lifting of a load and returnable to said unloaded position upon a substantial decrease of said pressure, exhibiting means operable under the control of said element each time there occurs said substantial changes of pressure for producing distinctive indications that a load has been lifted and lowered, and delay means for preventing movement in both directions of said element as be tween said loaded and said unloaded positions for preventing the recording of changes in the pressure of said hydraulic liquid due to operations other than the lifting and lowering of a pay load carried by said platform.

2. In a load-lifting apparatus having a fixed frame, a load-supporting platform and hydraulic means including a hydraulic liquid for raising and lowering said platform relative to said fixed frame, the combination of pressureresponsive means including a device fluid-connected to said hydraulic means, said device having an element displaceable from an unloaded position to a loaded position upon a substantial increase of pressure on said hydraulic liquid as occurs upon lifting of a load and returnable to said unloaded position upon a substantial decrease of said pressure, exhibiting means having an actuating arm operable under the control of said element in one direction upon an increase in pressure and in the opposite direction upon a decrease in pressure for producing distinctive indications thata load has been lifted and lowered, and delay means actuated in response to said changes in pressure for delaying displacement of said arm in one direction by a greater time interval than in the opposite direction whereby there are avoided false indications by said exhibiting means of the raising and lowering of pay loads.

3. The combination of claim 2 in which said exhibiting means includes a chart-carrying element, means for driving the chart at constant speed, a chart-marker for engaging said chart, and means operable in accordance with change of position of said arm for moving said marker relative to said chart for recording load-lifts made by said platform.

4. The combination set forth in claim 3 in which a second chart-marker is disposed for engagement with said chart, and means for moving said second chart-marker relative to said chart for recording thereon travel of the load-lifting apparatus with respect to time thereby to correlate the number of lifts with respect to time and with respect to the distance traveled by the load-lifting apparatus.

5. In a lifting truck having a fixed frame, a load-supporting platform and hydraulic means including a hydraulic liquid for raising and lowering said platform relative to said fixed frame, the combination of pressureresponsive means including a device which is fluid-connected to said hydraulic liquid, said device having an element displaceable from an unloaded position to a loaded position upon substantial change of pressure on said hydraulic liquid as occurs upon lifting of a load, indicating means operable under the control of said element each time there occurs said substantial change of pressure for producing a distinctive indication that a load has been lifted, and delay means for preventing return of said element from said loaded position to said unloaded position as a result of a transient decrease in said pressures on said hydraulic liquid, said delay means being ineffective to delay return of said element to said unloaded position after disappearance for a predetermined time interval of said substantial pressure on said hydraulic liquid, whereby there are avoided false indications by said indicating means of load-lifts by reason of travel of the truck over a rough surface with resultant transient loss of load on said platform. V

6. In a 1oad-lifting apparatus having a fixed frame, a load-supporting platform and hydraulic means including a hydraulic liquid for raising and lowering said platform relative to said fixed frame, the combination of pressure-responsive means including a device which is fluid-connected to said hydraulic means, said device having an'element displaceable from an unloaded position to a loaded position upon a substantial increase of pressure on said hydraulic liquid as occurs upon lifting of a load and returnable to said unloaded position upon a substantial decrease of said pressure, exhibiting means having an actuating arm operable under the control of said element each time there occurs said substantial changes of pressure for producing distinctive indications that a load has been lifted and lowered, and delay means actuated in response to said changes in pressure for delaying displacement of said arm from an unloaded position to a loaded position for a time interval less than the delay in the displacement of said arm from its loaded position to its unloaded position whereby there are avoided false indications by said exhibiting means of the raising and lowering of pay loads.

7. A recording system for use with a wheeled vehicular lifting apparatus having a lift platform, means for supplying hydraulic fluid under pressure for raising said platform and means for driving at least one wheel of said apparatus; said recording system including means for supporting and moving a chart at a fixed speed and in correlation With the passage of time, a stylus, means supporting said stylus for producing a record on said chart, means including a device responsive to said liquid pressure applied in raising and lowering the platform of the lifting apparatus and having an element displaceable from an unloaded position to a loaded position upon a substantial increase of pressure on the liquid as occurs upon lifting of the load and returning to said unloaded position upon a substantial decrease of the liquid pressure, a driving connection between said element and said stylus for producing distinctive indications on the chart that a load has been lifted and lowered, and delay means for preventing movement in both directions of said element as between said loaded and unloaded positions for preventing the recording of changes in the pressure of said hydraulic liquid due to operations other than the lifting and lowering of a pay-load carried by the lift platform of the vehicular apparatus.

8. The recording system of claim 7 in which a solenoid is connected to drive said stylus and in which said delay means includes time delay relays for regulating the movement of said stylus as between loaded and unloaded positions for preventing said recording of changes in the pressure of said hydraulic liquid due to operations other than the lifting and lowering of the payload carried by the lift platform of the lifting apparatus.

9. The recording system of claim 8 in which there is provided an energizing circuit for one of said time delay relays closed in response to operation of said pressureresponsive means, said last-named time delay relay having provisions for delaying its operation in one directionthereby to delay deenergization of the solenoid after energization thereof.

10. The recording system of claim 7 in which there is associated with said chart a second stylus for recording thereon the distance traveled by a wheel of the lifting apparatus, said pressure-responsive means including a pressure switch, a solenoid having a movable part forming said displaceable element and having a driving connection with said first-named stylus, an electrical circuit including said solenoid and said pressure switch, said delay means including a first time delay relay in said circuit operable to effect the delay between the closing of said pressure switch and the energization of said solenoid and a second time delay relay in said circuit operable to effect a delay between the opening of said pressure switch and the deenergization of said solenoid.

11. The recording system of claim 7 in which a second chart-marker is disposed for engagement with said chart, and means for moving said second chart-marker relative to said chart for recording thereon travel of the loadlifting apparatus with respect to time thereby to correlate the number of lifts with respect to time and with respect to the distance traveled by the load-lifting apparatus.

References Cited in the file of this patent UNITED STATES PATENTS 1,261,508 Gamble Apr. 2, 1918 2,307,961 Schellentrager Jan. 12, 1943 2,722,411 Philbrook Nov. 1, 1955 2,856,176 Cooper Oct. 14, 1958 2,883,177 Dannehl Apr. 21, 1959 

